Contextual memory and encoding strategies in young and older adults with and without depressive symptoms

Supraphysiologic doses of 17β-estradiol aggravate depression-like behaviors in ovariectomized mice possibly via regulating microglial responses and brain glycerophospholipid metabolism

BACKGROUND

17β-Estradiol (E2) is generally considered neuroprotective in humans. However, the current clinical use of estrogen replacement therapy (ERT) is based on the physiological dose of E2 to treat menopausal syndrome and has limited therapeutic efficacy. The efficacy and potential toxicity of superphysiological doses of ERT for menopausal neurodegeneration are unknown.

METHODS

In this study, we investigated the effect of E2 with a supraphysiologic dose (0.5 mg/kg, sE2) on the treatment of menopausal mouse models established by ovariectomy. We performed the open field, Y-maze spontaneous alternation, forced swim tests, and sucrose preference test to investigate behavioral alterations. Subsequently, the status of microglia and neurons was detected by immunohistochemistry, HE staining, and Nissl staining, respectively. Real-time PCR was used to detect neuroinflammatory cytokines in the hippocampus and cerebral cortex. Using mass spectrometry proteomics platform and LC-MS/ MS-based metabolomics platform, proteins and metabolites in brain tissues were extracted and analyzed. BV2 and HT22 cell lines and primary neurons and microglia were used to explore the underlying molecular mechanisms in vitro.

RESULTS

sE2 aggravated depression-like behavior in ovariectomized mice, caused microglia response, and increased proinflammatory cytokines in the cerebral cortex and hippocampus, as well as neuronal damage and glycerophospholipid metabolism imbalance. Subsequently, we demonstrated that sE2 induced the pro-inflammatory phenotype of microglia through ERα/NF-κB signaling pathway and downregulated the expression of cannabinoid receptor 1 in neuronal cells, which were important in the pathogenesis of depression.

CONCLUSION

These data suggest that sE2 may be nonhelpful or even detrimental to menopause-related depression, at least partly, by regulating microglial responses and glycerophospholipid metabolism.

Exploring Language Learning as a Potential Tool against Cognitive Impairment in Late-Life Depression: Two Meta-Analyses and Suggestions for Future Research

Late-life depression (LLD) affects about an eighth of community-dwelling seniors. LLD impacts well-being, with loneliness and small social networks being typical. It has also been linked to cognitive dysfunction and an increased risk of developing dementia. Safety and efficacy of pharmacological treatments for LLD have been debated, and cognitive dysfunction often persists even after remission. Various cognitive interventions have been proposed for LLD. Among these, one has received special attention: foreign language learning could serve as a social intervention that simultaneously targets brain structures affected in LLD. Lifelong bilingualism may significantly delay the onset of cognitive impairment symptoms by boosting cognitive reserve. Even late-life foreign language learning without lifelong bilingualism can train cognitive flexibility. It is then counterintuitive that the effects of language learning on LLD have never been examined. In order to create a theoretical basis for further interdisciplinary research, this paper presents a status quo of current work through two meta-analyses investigating cognitive functioning in LLD on the one hand and in senior bilinguals or seniors following a language course on the other hand. While LLD was consistently associated with cognitive dysfunction, inconsistent results were found for bilingualism and language learners. Possible reasons for this and suggestions for future research are subsequently discussed.

Episodic memory boosting in older adults: exploring the association of encoding strategies and physical activity

Background: Contextual memory is susceptible to the effects of aging and its impairment compromises episodic memories and quality of life in older adults. Objective: Compare the effects of cognitive support on incidental contextual memory free recall and recognition with a naturalistic experimental paradigm and explore the association of encoding strategies and physical activity on memory improvement. Methods: Subjects (≥60 years, n = 52) were assigned to one of two encoding conditions for the contextual memory task: with or without an incidental associative instruction to encourage association of an item to its spatial context. Immediate free recall and recognition tests were run to assess the encoding instruction efficiency. The association of memory performance and physical activity was analyzed using the scores on the International Physical Activity Questionnaire (IPAQ) to subdivide each experimental group into Low IPAQ (below median) and High IPAQ (above median) subgroups. Results: The associative encoding instruction increased contextual memory free recall and recognition, with greater effects on free recall. The most robust associations between physical activity and contextual memory were also seen on free recall, in which higher levels of physical activity corresponded to increased baseline performance (non-associative encoding condition) and greater improvement of memory by the encoding support (associative encoding condition). Conclusion: Cognitive support at encoding can improve contextual memory free recall and recognition, suggesting they are prone to rehabilitation. Moreover, higher physical activity levels were positively associated with encoding strategies on contextual memory improvement, increasing the availability of latent process-based components of the cognitive reserve.

Mental health in familial caregivers of Alzheimer's disease patients: are the effects of chronic stress on cognition inevitable?

Familial caregivers of Alzheimer's disease (AD) patients experience an emotional and physical burden which characterizes a chronic stress condition. The resulting hypothalamic-pituitary-adrenal axis dysfunction favors an imbalance of neurotoxic/neuroprotective factors and causes cognitive impairments, increasing the caregivers' risk for cognitive decline and compromising their ability to provide adequate care of the patient. Therefore, the present study aimed to investigate the reversibility of the cognitive impairments of familial caregivers of AD patients during their caregiving-related chronic stress condition. Thirty-three caregivers (61.42 + 2.68 years; 27 women) and thirty-four controls (57.91 ± 2.16 years, 20 women) were evaluated for their cognitive functioning (attention, executive function, processing speed and memory) with a neuropsychological battery (Digit-span, Trail Making, Stroop and the Logical Memory tests). Subjects' cortisol/dehydroepiandrosterone (DHEA) ratios were determined by radioimmunoassay, and their brain-derived neurotrophic factor (BDNF) levels were analyzed by ELISA. An incidental contextual memory task, with or without an associative encoding instruction, was used to investigate if caregivers have a cognitive reserve prone to rehabilitation. The contextual memory impairment of caregivers was associated with prefrontal and hippocampal cognitive dysfunctions, alterations of the cortisol/DHEA ratio and lower BDNF levels. Even so, the contextual memory impairment could be improved by the associative encoding condition. This study suggests that the cognitive impairments of caregivers are not necessarily irreversible, as indicated by the results obtained for contextual memory, which could be improved despite the ongoing chronic stress and associated hormonal and neurotrophin dysfunctions. Lay summary The support of a relative with Alzheimer's Disease submits the familial caregivers to a chronic stress condition that increases their own risk of cognitive decline. This study suggests that, irrespective to their alterations on cortisol/DHEA ratio and BDNF levels, caregivers have a cognitive reserve that could probably be engaged to limit the negative effects of chronic stress on cognition.

Relate it! Objective and subjective evaluation of mediator-based strategies for improving source memory in younger and older adults

The present study examined younger and older adults' ability to improve their source memory for different types of sources through imaginal and verbal (sentence) mediators. Younger (18-29 years) and older (60-75 years) adults' strategy use and source memory for either text-type (bold vs italic) or person (woman vs man) sources was assessed; strategy use was either spontaneous or the generation of imaginal mediators was instructed before encoding. Younger and older adults did not differ in spontaneous use of mediator-based strategies; however, older adults generated more images but fewer verbal mediators than younger adults. Participants were able to increase mediator generation when instructed to, resulting in substantial increases in both item and source memory for the instructed conditions in both age groups. Use of verbal mediators was more likely for the more concrete person sources for which source memory was generally better. Importantly, these objective benefits of mediator-based strategies translated into subjective benefits for both younger and older adults: Increased use of either mediator type was correlated with lower experienced task difficulty; the instructions to use imaginal mediators resulted in a significant decrease in difficulty ratings on the group level. Participants were generally able to monitor mediator benefits to both item and source memory and accurately judged mediator strategies (especially imagery) as more effective than repetition; older adults, however, rated all strategies as less effective than younger adults. Implications of these findings, especially for neuropsychological studies on source monitoring, are discussed.

The role of encoding strategies in contextual memory deficits in patients with bipolar disorder

Contextual memory is important for the encoding and retrieval of episodic memory, which is often impaired in euthymic patients with bipolar disorder (BD). The objective was to investigate the effect of low and high cognitive support on encoding in an incidental contextual memory task in euthymic patients with BD. Twenty-three patients with a BD type I diagnosis (aged 23-63 years, 17 women and 6 men) and 29 healthy controls completed a recognition memory task for context (location of a recognised object). Participants were assigned to one of two incidental encoding conditions: (1) with a binding cue to encourage the association of the object to its location (judging the degree of appropriateness of an object in relation to its location) or (2) without a binding cue (judging daily use of objects). Patients showed a deficit in incidental contextual memory in the absence of a binding cue at encoding. Under incidental encoding with the binding cue, no differences were observed between the groups for contextual memory. Contextual memory deficits in BD patients were reduced by providing cognitive support at encoding. The role of this strategy should be investigated in larger samples to evaluate its use for cognitive remediation in BD patients.

Effects of similarity on environmental context cueing

Three experiments examined the prediction that context cues which are similar to study contexts can facilitate episodic recall, even if those cues are never seen before the recall test. Environmental context cueing effects have typically produced such small effect sizes that influences of moderating factors, such as the similarity between encoding and retrieval contexts, would be difficult to observe experimentally. Videos of environmental contexts, however, can be used to produce powerful context-dependent memory effects, particularly when only one memory target is associated with each video context, intentional item-context encoding is encouraged, and free recall tests are used. Experiment 1 showed that a not previously viewed video of the study context provided an effective recall cue, although it was not as effective as the originally viewed video context. Experiments 2 and 3 showed that videos of environments that were conceptually similar to encoding contexts (e.g., both were videos of ball field games) also cued recall, but not as well if the encoding contexts were given specific labels (e.g., "home run") incompatible with test contexts (e.g., a soccer scene). A fourth experiment that used incidental item-context encoding showed that video context reinstatement has a robust effect on paired associate memory, indicating that the video context reinstatement effect does not depend on interactive item-context encoding or free recall testing.

Subjective mild depressive symptoms are associated with abnormal diurnal cycle of salivary cortisol in older adults

BACKGROUND

Alterations in cortisol secretion pattern seem to be involved in the associations between aging, depression, and cognitive decline.

OBJECTIVE

The aim of this study was to mainly assess cortisol circadian profile in older adults with subjective depressive symptoms.

METHODS

Salivary cortisol samples from healthy young (n = 22) and old adults (n = 22), and from older adults who self-reported depressive symptoms in Geriatric Depression Scale (n = 22) were collected at 7 AM, 4 PM, and 10 PM and were analyzed by radioimmunoassay.

RESULTS

Older adults with depressive symptoms presented the characteristic cortisol circadian pattern, but they showed higher cortisol levels at 10 PM than healthy young and elderly controls.

CONCLUSIONS

Our data suggest that mild depressive symptoms could be associated with a cortisol secretion pattern previously described as being predictive of cognitive decline.

Incidental Encoding Strategies Did Not Improve Contextual Memory in Parkinson’s Disease Patients

Background. This study investigated the performance of patients with idiopathic Parkinson’s disease (PD) without dementia for incidental recognition memory and the effect of encoding strategies on contextual memory. Methods. The authors studied 21 patients with PD (ages 60-85, 12 women; Hoehn and Yahr I-III, Activities of Daily Living 70%-100%) and 22 healthy controls (ages 60-84, 18 women). Participants completed the vocabulary subtest of the Wechsler Adult Intelligence Scale and the Wisconsin Card Sorting Test (WCST). To assess the incidental recognition memory for item (object) and context (location of the object), participants of each group were assigned to 1 of 2 encoding conditions: ( a) an incidental associative instruction to bind the object to its location or ( b) a nonassociative, nonspecific instruction. Results. PD patients showed performance comparable to the control group’s on the vocabulary subtest and WCST. In contrast to controls, PD patients were unable to take advantage of the associative encoding instruction, which also had a deleterious effect on item recognition. Conclusion. This sample of participants with PD showed diminished item and context recognition memory and an impaired ability to use incidental memory encoding strategy, suggesting a compromised cognitive reserve. The fact that these alterations occurred in early stages of PD, and prior to more general cognitive alterations such as executive dysfunction, should be considered in the management of patients by using specific cognitive rehabilitation interventions.